Answer
a) $f(0)=4$
b) $f\left( -3 \right)=0\,\,\text{and}\,\,f\left( 3 \right)=0$.
Work Step by Step
(a)
It can be seen from the graph that the function f has a relative maximum at 0 with the value 4.
(b)
We can see that the function f has a relative minimum at −3 and 3.
The value of the relative minimum is $f\left( -3 \right)=0\,\,\text{and}\,\,f\left( 3 \right)=0$.